Process for enhancing the fuel value of low BTU gas

ABSTRACT

In the field of chemical fuels, prior art coal gasification produces a fuel value of a mixture of carbon monoxide and hydrogen which has a lower BTU than methane. The present process uses coal resources more economically for industry by converting part of the hydrogen and part of the carbon in the carbon monoxide of the gas mixture to methane, by continuously introducing the gas mixture into a fluid bed in the presence of iron under conditions of pressure and temperature which promote the reduction of carbon monoxide to carbon, the formation of iron carbide from the iron and carbon, and the formation of methane and iron from iron carbide and hydrogen, and continuously removing from the fluid bed a methane enriched gas mixture including carbon monoxide and hydrogen having a substantially increased fuel value over the gas mixture introduced into the fluid bed.

DESCRIPTION

This application is a continuation-in-part of my copending application,U.S. Ser. No. 817,576, filed July 21, 1977 now U.S. Pat. No. 4,134,907.

TECHNICAL FIELD

The need to use the extensive coal resources in this country as a sourceof fuel gas is now quite evident in view of the rapid depletion of othersources. Accordingly, it has become essential to develop processes forthe economic production of fuel gas for industrial uses from coal.

Atmospheric coal gasification processes are well known and welldeveloped. Typical of these proven processes are the Koppers-Totzek,Winkler, Wellman-Galusha, Woodall-Duckman, and others. The gas producedfrom these gasification processes is a low BTU gas comprising a mixtureof carbon monoxide and hydrogen. This gas mixture has a low fuel valueof about 300 Btu/ft³ or less, on the average, which is too low for mostindustrial uses.

The fuel value of the gas produced by the atmospheric coal gasificationprocesses can be enhanced with the use of high temperatures andpressures, sometimes accompanied by the use of oxygen and/or catalysts,to make the hydrogen and carbon monoxide present react to producemethane. Methane has a heat of combustion of 1013 Btu/ft³, whereascarbon monoxide and hydrogen has Btu's of about 322 and 325,respectively. The chief disadvantage, of course, of these procedures forenhancing the fuel value of the low Btu gas is the expense involved. Theexpense is so great that low Btu gas enhanced in this manner is notcompetitive with other fuels available for industrial uses.

So-called intermediate Btu gas is suitable for industrial uses, this gashaving a Btu value of 450 Btu/ft³ or more. It will burn well in existinggas burner equipment in power plants and other industrial applicationswith only minor modification in the burner head. The Btu value is highenough so that its use does not result in loss of boiler efficiency and,further, this gas can be economically piped moderate distances, which isnot true for low Btu gas.

Accordingly, it is an object of this invention to provide a relativelyinexpensive process for enhancing the fuel value of the low Btu gasproduced by coal gasification processes.

DISCLOSURE OF THE INVENTION

A process for increasing the fuel value of a gas mixture of carbonmonoxide and hydrogen by converting part of the hydrogen, and part ofthe carbon in the carbon monoxide of the gas mixture to methane, whichcomprises continuously introducing the gas mixture into a fluid bed inthe presence of a mixture of iron and iron carbide under conditions ofpressure and temperature which promote the reduction of carbon monoxideto carbon along with the formation of iron carbide by the reaction ofiron and carbon followed by the formation of methane and iron by thereaction of iron carbide with hydrogen, while continuously removing fromthe fluid bed a gas mixture including methane, carbon monoxide andhydrogen having a substantially increased fuel value over the gasmixture introduced into the fluid bed. The gas mixture removed has a Btuvalue of about 600 on the average and is a suitable industrial orutility fuel. If methane alone is required it can be recovered from thegas mixture removed from the fluid bed by conventional procedures.

BRIEF DESCRIPTION OF DRAWINGS

FIGS. 1-3 are stability diagrams indicating the gas phase relationshipsbetween iron carbide and the hydrogen-carbon-oxygen system. The symbolαC refers to the activity of carbon in the system. The symbol "P"represents partial pressure. The amounts of gases are essentiallydirectly related to the partial pressures.

BEST MODE FOR CARRYING OUT THE INVENTION

The invention is based on establishing and maintaining conditions in afluid bed which promote the following three reactions:

(1) CO+H₂ →C+H₂ O

(2) C+3Fe→Fe₃ C

(3) Fe₃ C+2H₂ →3Fe+CH₄

These reactions will proceed under atmospheric pressures, althoughslightly elevated pressures may be preferred.

In the fluid bed reaction, the iron acts as an acceptor of carbon inreaction (2) and as a donor of carbon in reaction (3). It will be notedthat iron is reformed or regenerated in reaction (3) and that the ironcarbide is reformed or regenerated in reaction (2) so that after thefirst addition of iron and iron carbide they are always present in thereaction zone without further additions.

Reaction (3) can be made to proceed to the right either by the additionof hydrogen or the removal of methane. Hydrogen and carbon monoxide arebeing continuously added in reaction (1) and methane, along with thecarbon monoxide and hydrogen not converted, is being continuouslyremoved as part of the enriched fuel gas.

The reactions can be made to proceed and controlled by controlling theratio of the various gases present, that is, the ratio of methane tohydrogen, water to hydrogen, carbon dioxide to carbon monoxide, etc.Charts will be described hereinafter illustrating how control of theseratios results in the reactions proceeding in the required manner.

The fluidized bed reactor referred to herein is of the conventional typein which finely divided feed material on a grate or perforate support isfluidized by upwardly flowing gases which may include or entirelycomprise the reactant gases. Auxiliary equipment includes heating andtemperature control and monitoring equipment, heat exchangers,scrubbers, cyclones, gas cycling equipment and other conventionalequipment which is used to remove solids from the off-gas stream and toremove water and CO₂ from a recycle gas loop to shift the gas systemequilibrium.

The reactants introduced into the reactor after the initial charge ofiron carbide and iron are the low Btu coal gasification gases containingcarbon monoxide and hydrogen.

By proper balancing of the ratios of the hydrogen and carbon bearingmaterials in accordance with the stability diagrams, it is possible tomake the hydrogen serve a reducing function to reduce the carbonmonoxide to carbon, and the carbon serve a carburizing function as ironcarbide is formed. As stated previously, conditions are established andmaintained so that iron serves both a carbon acceptor function and acarbon donor function. Additionally, reaction conditions are adjusted sothat hydrogen performs an additional reducing function in reducing ironcarbide to iron and forming methane with the released carbon.

Because of the equilibrium conditions involved in hydrogen-carbon-oxygengas systems, the required hydrogen-carbon ratios will automaticallyrequire that methane be present in the gas system. The quantity ofmethane present or produced will be a function of carbon to hydrogenratios, as well as temperature and pressure conditions, and all of thesecan be controlled.

FIGS. 1, 2 and 3 are stability diagrams indicating the gas phaserelationships between iron carbide and the hydrogen-carbon-oxygen systemat temperatures of 1160°, 1070° and 1250° F., respectively. Thestability diagrams indicate the relationship between log plots ofpartial pressure ratios of the various gas components which are inequilibrium with iron carbide in the present process. These illustratethat definite amounts of methane will exist in the system in thepresence of the iron carbide, and that the amount of methane present orproduced can be controlled by controlling the other variables in thesystem. These stability diagrams show that for any given temperature andpressure there is a fixed relationship between the gas components andthe solid reactants iron and iron carbide thus indicating that fixed gascompositions will be obtained if mixed gases are contacted with ironcarbide. Furthermore, the equilibrium gas composition can be altered atany given temperature and pressure by removal of one or more reactionproducts from the system. For example, if water vapor and/or carbondioxide are continuously removed by scrubbing in the recycle gas loop,then the quantity of methane will continue to increase in the reactionzone. The charts indicate the operative range of variables at specifiedtemperatures for insuring that Fe₃ C is present in the fluid bed. Theyalso show the effect of temperature on the production of methane and Fe₃C when the other variables for insuring the presence of Fe₃ C in thefluid bed are maintained substantially constant.

A feasible temperature range for the process is about 600° F. to about1200° F., preferably about 600° F. to about 950° F. Temperatures outsidethese ranges are not economically feasible. Atmospheric pressures can beused and are preferred, although slightly elevated pressures of up toabout 10 atmospheres are also suitable. Higher pressures areuneconomical.

The iron to iron carbide ratio in the reaction area can vary betweenabout 10 percent iron carbide to 96 percent or more iron carbide. Ironmay be added in metallic form or supplied from various sources,including iron oxide. Some carbon dioxide can be used in the feed gas asa source of carbon. It is an advantage of the process that oxygen isremoved from the process in the form of water which is easily recovered.If any methane is fed into the reactor, it is unreacted and recoveredwith the product gas.

A 50 percent mixture of methane with carbon monoxide and hydrogen givesa gas mixture of 600 Btu. As can be seen from the examples below, thisintermediate fuel gas is easily produced by the process of theinvention.

EXAMPLE 1

Using the stability diagrams, a computer program was constructed whichgives the equilibrium gas composition expected for the process whenvarious hydrogen and carbon bearing gases are contacted with iron-ironcarbide mixtures at various temperatures. Table 1 below shows examplesof results obtained from this computer program under varying conditionsof inlet gas composition, temperature and pressure under which theprocess is performed within the favorable methane production gas ratiosillustrated in FIGS. 1-3.

                                      TABLE 1                                     __________________________________________________________________________     Equilibrium Shift Calculations for Fe.sub.3 C System                         Pres-                                    Btu/scf                              Temp                                                                              sure                                                                             Inlet Gas, Volume Percent                                                                      Off-gas, Volume Percent                                                                        Inlet                                                                            Off                               °F.                                                                        Atm                                                                              H.sub.2                                                                          H.sub.2 O                                                                        CO CO.sub.2                                                                         CH.sub.4                                                                         N.sub.2                                                                         H.sub.2                                                                          H.sub.2 O                                                                        CO CO.sub.2                                                                         CH.sub.4                                                                         N.sub.2                                                                         Gas                                                                              Gas                               __________________________________________________________________________    Section 1                                                                     750  1 48.0                                                                             2.0                                                                              39.0                                                                             5.0                                                                              1.0                                                                              5.0                                                                             4.6                                                                              9.7                                                                              1.7                                                                              38.0                                                                             37.5                                                                             8.6                                                                             292                                                                              434                               840 1  48.0                                                                             2.0                                                                              39.0                                                                             5.0                                                                              1.0                                                                              5.0                                                                             8.0                                                                              9.0                                                                              4.5                                                                              35.6                                                                             34.7                                                                             8.3                                                                             292                                                                              422                               930 1  48.0                                                                             2.0                                                                              39.0                                                                             5.0                                                                              1.0                                                                              5.0                                                                             13.0                                                                             8.5                                                                              9.7                                                                              30.9                                                                             30.0                                                                             7.8                                                                             292                                                                              405                               1020                                                                              1  48.0                                                                             2.0                                                                              39.0                                                                             5.0                                                                              1.0                                                                              5.0                                                                             19.8                                                                             8.0                                                                              17.1                                                                             24.2                                                                             23.6                                                                             7.2                                                                             292                                                                              382                               1110                                                                              1  48.0                                                                             2.0                                                                              39.0                                                                             5.0                                                                              1.0                                                                              5.0                                                                             27.9                                                                             7.1                                                                              25.2                                                                             17.0                                                                             16.3                                                                             6.5                                                                             292                                                                              356                               1200                                                                              1  48.0                                                                             2.0                                                                              39.0                                                                             5.0                                                                              1.0                                                                              5.0                                                                             35.6                                                                             5.9                                                                              32.1                                                                             10.8                                                                             9.7                                                                              5.8                                                                             292                                                                              331                               1290                                                                              1  48.0                                                                             2.0                                                                              39.0                                                                             5.0                                                                              1.0                                                                              5.0                                                                             41.6                                                                             4.6                                                                              36.8                                                                             6.7                                                                              4.9                                                                              5.4                                                                             292                                                                              312                               Section 2                                                                     750 1  53.0                                                                             1.0                                                                              31.0                                                                             1.0                                                                              13.0                                                                             1.0                                                                             7.7                                                                              16.4                                                                             0.9                                                                              19.4                                                                             54.0                                                                             1.7                                                                             400                                                                              674                               840 1  53.0                                                                             1.0                                                                              31.0                                                                             1.0                                                                              13.0                                                                             1.0                                                                             12.7                                                                             14.0                                                                             2.5                                                                              18.9                                                                             50.0                                                                             1.6                                                                             400                                                                              638                               930 1  53.0                                                                             1.0                                                                              31.0                                                                             1.0                                                                              13.0                                                                             1.0                                                                             19.3                                                                             11.4                                                                             5.9                                                                              17.0                                                                             44.9                                                                             1.5                                                                             400                                                                              595                               Section 3                                                                     930 1  48.0                                                                             2.0                                                                              39.0                                                                             5.0                                                                              1.0                                                                              5.0                                                                             13.0                                                                             8.5                                                                              9.7                                                                              30.9                                                                             30.0                                                                             7.8                                                                             292                                                                              405                               930 5  48.0                                                                             2.0                                                                              39.0                                                                             5.0                                                                              1.0                                                                              5.0                                                                             6.3                                                                              10.0                                                                             4.6                                                                              35.4                                                                             35.3                                                                             8.4                                                                             292                                                                              429                               930 10 48.0                                                                             2.0                                                                              39.0                                                                             5.0                                                                              1.0                                                                              5.0                                                                             4.6                                                                              10.4                                                                             3.3                                                                              36.5                                                                             36.7                                                                             8.5                                                                             292                                                                              435                               __________________________________________________________________________

The results recorded in section 1 of Table 1 show the theoretical changein composition resulting when a gas having a composition similar tocommercially produced "blue water gas" is subjected to the computerizedprogram.

The results is section 2 of the Table show the theoretical change incomposition obtained when a gas having a composition similar to gasproduced by the Lurgi oxygen-pressure gasification is subjected to thecomputerized process. The large increase in yields of methane within awell defined temperature range graphically illustrates the criticaleffect of temperature on the yield of methane.

The results in section 3 of the Table show the theoretical effect ofpressure on the yield of methane when the computerized process isapplied to the same gas used for the section 1 tests. Methane yield isincreased from 30 volume percent to 36.7 volume percent by increasingthe pressure from one to ten atmospheres. Increased pressures wouldprobably show slight increase in methane production but such pressuresbecome uneconomic.

EXAMPLE 2

In order to further illustrate the operativeness of the invention and toillustrate the correlation between the results obtained by the computerapplication of the process and actual operation of the process, benchscale tests were made of the process. The tests were run in accordancewith previously described procedure. Adequate iron and iron carbide werepresent in the fluid bed to start the reaction. No further addition ofthese components was necessary. Results from actual tests are recordedin each section with results from the computerized test under identicalconditions. The results are recorded in Table 2.

                                      TABLE 2                                     __________________________________________________________________________     Experimental Shift Data for Fe.sub.3 C System                                                                                    Btu/scf                   Temp       Pressure                                                                           Inlet Gas, Volume Percent                                                                       Off-gas, Volume Percent                                                                         Inlet                                                                            Off-                   °F. Atm  H.sub.2                                                                          H.sub.2 O                                                                        CO CO.sub.2                                                                         CH.sub.4                                                                         N.sub.2                                                                          H.sub.2                                                                          H.sub.2 O                                                                        Co CO.sub.2                                                                         CH.sub.4                                                                         N.sub.2                                                                          Gas                                                                              Gas                    __________________________________________________________________________    Section 1                                                                     Actual                                                                              1020 1    65.0                                                                             2.0                                                                              33.0                                                                             0  0  0  60.7                                                                             2.5                                                                              12.6                                                                             2.4                                                                              21.8                                                                             0  317                                                                              461                    Computer                                                                            1020 1    65.0                                                                             2.0                                                                              33.0                                                                             0  0  0  38.8                                                                             1.7                                                                              10.5                                                                             17.2                                                                             31.8                                                                             0  317                                                                              481                    Section 2                                                                     Actual                                                                              1020 1    22.0                                                                             1.7                                                                              17.7                                                                             13.3                                                                             7.8                                                                              37.5                                                                             30.2                                                                             1.1                                                                              13.0                                                                             4.8                                                                              12.5                                                                             38.4                                                                             207                                                                              264                    Computer                                                                            1020 1    22.0                                                                             1.7                                                                              17.7                                                                             13.3                                                                             7.8                                                                              37.5                                                                             15.9                                                                             1.9                                                                              16.2                                                                             5.7                                                                              13.3                                                                             47.0                                                                             207                                                                              239                    __________________________________________________________________________

The results recorded in section 1 of Table 2 are from a test programusing a 3:1 mixture of hydrogen to carbon monoxide as the inlet gas,this gas representing a gasification process working with oxygen. At1020° F. the actual test produced a gas with a 21.8 percent methane anda Btu value of 461 as compared to the predicted values of 31.8 percentmethane and 481 Btu's.

The results recorded in section 2 of Table 2 show the change incomposition obtained by the process in a representative gas containingrelatively large amounts of inert nitrogen, this gas representing agasification process working with air. The actual test produced a gaswith 12.5 percent methane and a Btu value of 264 as compared to apredicted methane content of 13.3 percent and a Btu value of 239. Anincrease in Btu value of over 30 percent was obtained in both instances.

The test results established the operativeness of the process forproducing methane, and prove the validity of the stability diagrams ofFIGS. 1-3 for use in selecting conditions for operative and feasibleproduction of methane.

EXAMPLE 3

Various gases were fed at a rate of 200 cubic feet per minute to a twofoot diameter fluidized-bed reactor containing sufficient iron and ironcarbide to start the reaction. No further addition of these materialswas necessary. The inlet gases consisted of hydrogen, carbon monoxideand carbon dioxide introduced in amounts conforming to favorable methaneproduction ratios illustrated in FIGS. 1-3. A temperature of 930° F. andatmospheric pressure were used for all the tests. The inlet gas had acomposition of approximately 82 percent hydrogen, 8 percent carbondioxide and 10 percent methane with a Btu value of about 370. The ratioof iron carbide to iron varied from a ratio of about 73/27 percent to96/4 percent.

Analyses were made of the off-gas taken at half-hour intervals for a 12hour period, the results of which are presented in Table 3.

                  TABLe 3                                                         ______________________________________                                         Pilot Plant Gas Composition Data                                             Reactor Products-Solid, Gas                                                                         Ratio                                                   Off Gas                 CO/    H.sub.2 /                                                                            H.sub.2 /                               Time H.sub.2 O                                                                            CO.sub.2                                                                             CO   N.sub.2                                                                            H.sub.2                                                                            CH.sub.4                                                                            CO.sub.2                                                                           H.sub.2 O                                                                          CH.sub.3                    ______________________________________                                        2400 1.2    4.5    3.9  8    35   44    0.9  29.2 0.8                         0030 1.2    4.5    3.9  8    33   44    0.9  27.5 0.8                         0100 1.0    4.5    3.9  8    35   44    0.9  35.0 0.8                         0130 1.0    4.8    4.2  8    35   43    0.9  35.0 0.8                         0200 1.0    4.8    4.2  8    35   44    0.9  35.0 0.8                         0230 1.0    4.8    4.2  8    35   44    0.9  35.0 0.8                         0300 1.0    4.8    4.0  8    34   42    0.8  34.0 0.8                         0330 1.0    4.8    4.2  8    34   43    0.9  34.0 0.8                         0400 1.0    4.8    4.2  8    34   43    0.9  34.0 0.8                         0430 1.0    5.5    4.2  8    35   43    0.8  35.0 0.8                         0500 1.0    5.5    4.0  8    35   43    0.7  35.0 0.8                         0530 1.0    6.7    4.8  8    35   40    0.7  35.0 0.9                         0600 1.0    6.2    4.8  8    35   40    0.8  35.0 0.9                         0630 1.0    6.2    4.8  8    35   41    0.8  35.0 0.9                         0700 1.0    6.2    5.0  8    35   40    0.8  35.0 0.9                         0730 1.0    6.7    5.1  8    35   40    0.8  35.0 0.9                         0800 2.4    7.5    7.9  7    35   40    1.1  14.6 0.9                         0830 2.4    7.75   8.25 6.5  35   39    1.1  14.6 0.9                         0900 2.4    8.6    8.9  7    34   38.3  1.0  14.2 0.9                         0930 2.4    5.3    6.6  7    38   40    1.3  15.8 1.0                         1000 2.3    4.4    4.5  5.5  41   33.5  1.0  17.8 1.2                         1030 2.3    3.6    4.5  5.5  40   40    1.3  17.4 1.0                         1100 2.4    4.5    5.2  7    39   41.5  1.2  16.3 0.9                         1130 2.3    4.8    6.5  7    37   41.5  1.4  16.1 0.9                         ______________________________________                                    

The average methane content of the off-gas during the 12-hour periodexceeded 40 percent and the off-gas had a Btu average value of about 560as compared to the Btu value of only 370 for the inlet gas.

Again, the results of the table show the feasibility of the process forstrongly enhancing the Btu value of a gas, including one containingmethane. The results illustrate the feasible time period for theenhancement. Further, the results show that large amounts of methane areproduced with large percentages of iron carbide to iron present in thefluid bed. For example, at 1000 the percentage of iron carbide to ironin the bed was about 96 percent. The results further establish thevalidity of the stability diagrams of FIGS. 1-3 for use in selectingfavorable operating conditions for the process.

EXAMPLE 4

Gases containing hydrogen and carbon monoxide in a ratio of three partsof hydrogen to one part of carbon monoxide were fed at a rate of 200cubic feet to a two-foot diameter fluidized-bed reactor containingsufficient iron and iron carbide to start the reaction. No furtheraddition of these materials was necessary. A temperature of 840° F. andatmospheric pressure were used for all tests. After the system reachedequilibrium with respect to off-gas composition, a portion of theoff-gas was taken through a water scrubbing step to remove the waterformed in the reaction and this scrubbed gas was substituted for part ofthe incoming hydrogen and carbon monoxide feed gas. As predicted fromthe stability diagrams, this removal of water shifted the equilibriumand permitted additional quantities of hydrogen and carbon monoxide toreact and form methane. Analysis of the off-gas taken at half-hourintervals for a period of twelve hours are presented in Table 4.

                                      TABLE 4                                     __________________________________________________________________________    Pilot Plant Gas Composition Data                                              for Reactor Products with Water Scrub Circuit                                 Off-gas             Recycle Gas                                                                          Ratio                                              Time                                                                             H.sub.2 O                                                                        CO.sub.2                                                                         CO N.sub.2                                                                          H.sub.2                                                                         CH.sub.4                                                                         H.sub.2 O                                                                            CO/CO.sub.2                                                                        H.sub.2 /H.sub.2 O                                                                 H.sub.2 /CH.sub.4                        __________________________________________________________________________    1800                                                                             8  6  4  10 32                                                                              40 3      0.7  4.0  0.8                                      1900                                                                             8  6  4  8  31                                                                              42 3      0.7  3.9  0.7                                      2000                                                                             8  6  5  7  29                                                                              44 3      0.9  3.6  0.7                                      2100                                                                             8  6  5  5  26                                                                              48 3      0.9  3.3  0.5                                      2200                                                                             8  6  5  3  24                                                                              52 3      0.9  3.0  0.5                                      2300                                                                             8  6  5  4  24                                                                              52 3      0.9  3.0  0.5                                      2400                                                                             7  4  5  4  22                                                                              56 2      1.3  3.1  0.4                                      0100                                                                             7  4  4  4  20                                                                              60 2      1.0  2.9  0.3                                      0200                                                                             6  5  5  4  22                                                                              58 2      1.0  3.7  0.4                                      0300                                                                             7  4  4  4  20                                                                              60 2      1.0  2.9  0.3                                      0400                                                                             6  4  3  4  20                                                                              62 2      0.8  3.3  0.3                                      0500                                                                             6  5  3  3  20                                                                              62 2      0.6  3.3  0.3                                      0600                                                                             6  5  3  3  20                                                                              62 2      0.6  3.3  0.3                                      __________________________________________________________________________

The average methane content of the gas increased from 42 percent at thebeginning of the run to a value of 62 percent at the end of the run togive an increased Btu value of 690 as compared to the 300 Btu value ofthe inlet gas. By shifting the equilibrium through the removal of watervapor, the methane content was increased as indicated by the stabilitydiagrams.

Similar results were obtained when the equilibrium was shifted byremoving CO₂ from the recycle gas through the addition of caustic to thewater scrub recycle loop. These results further establish the validityof the stability diagrams of FIGS. 1-3 for use in selecting favorableoperating conditions for the process.

I claim:
 1. A process for producing methane in a single reaction zone inthe presence of iron, Fe₃ C, carbon monoxide, carbon dioxide, hydrogenand water comprising:(a) maintaining in a fluidized bed, iron and Fe₃ Cin a single reactor without substantial further additions of iron and/orFe₃ C to the reactor; (b) introducing a gas mixture containing carbonmonoxide and hydrogen into the reactor; (c) reacting the iron and Fe₃ Cwith the carbon monoxide and hydrogen and balancing the ratio of carbonmonoxide, hydrogen, carbon dioxide, water and methane under conditionssuch that a portion of the carbon monoxide is reduced to carbon, iron isreacted with the carbon to produce Fe₃ C, and the Fe₃ C is reacted withhydrogen to form methane and reform iron; (d) removing water and/orcarbon dioxide; via a recycle gas stream; and (e) recovering methanefrom the reactor.
 2. The process of claim 1 wherein the reaction isconducted at a temperature of from about 600° F. to about 1200° F. 3.The process of claim 1 wherein the reaction is conducted from about 600°F. to about 950° F.
 4. The process of claim 1 wherein the reaction isconducted at a pressure of from about 1 to about 10 atmospheres.
 5. Theprocess of claim 1 wherein methane is recovered in continuous fashionfrom the reactor.
 6. The process of claim 1 wherein carbon dioxide isadded to the reactor as a source of carbon.
 7. The process of claim 1wherein water is removed from the reactor via a recycle gas stream. 8.The process of claim 7 wherein the water is continuously removed.
 9. Theprocess of claim 1 wherein carbon dioxide is removed via a recycle gasstream.
 10. The process of claim 9 wherein the carbon dioxide iscontinuously removed.
 11. The process of claim 2 wherein the reaction isconducted at a pressure of from about 1 to about 10 atmospheres.
 12. Theprocess of claim 2 wherein methane is recovered in continuous fashionfrom the reactor.
 13. The process of claim 2 wherein carbon dioxide isadded to the reactor as a source of carbon.
 14. The process of claim 2wherein water is removed from the reactor via a recycle gas stream. 15.The process of claim 2 wherein the water is continuously removed. 16.The process of claim 2 wherein carbon dioxide is removed via a recyclegas stream.
 17. The process of claim 16 wherein the carbon dioxide iscontinuously removed.
 18. The process of claim 4 wherein methane isrecovered in continuous fashion from the reactor.
 19. The process ofclaim 4 wherein the water and/or carbon dioxide is removed during thereaction by means of a recycle gas stream.
 20. The process of claim 4wherein carbon dioxide is added to the reactor as a source of carbon.21. The process of claim 4 wherein water is removed from the reactor viaa recycle gas stream.
 22. The process of claim 21 wherein the water iscontinuously removed.
 23. The process of claim 4 wherein carbon dioxideis removed via a recycle gas stream.
 24. The process of claim 23 whereinthe carbon dioxide is continuously removed.
 25. A process for convertinga first gas mixture containing carbon monoxide and hydrogen into asecond gas mixture of methane, carbon monoxide and hydrogen having asubstantially increased fuel value over said first gas mixture in asingle reaction zone which comprises,(a) maintaining iron and Fe₃ C in afluidized bed in the reaction zone without substantial further additionsof iron and/or Fe₃ C to the reaction zone; (b) continuously introducingsaid first gas mixture into said fluidized bed in the reaction zone; (c)adjusting gas compositions in the reaction zone by a circulating gasstream which removes water and/or carbon dioxide so as to maintainmixtures of carbon monoxide, carbon dioxide, hydrogen, water and methanewhich are thermodynamically favorable for maintaining the presence ofFe₃ C and the formation of methane; (d) continuously removing from saidreaction zone as a product said second gas mixture of methane, carbonmonoxide and hydrogen having an increased fuel value.
 26. The process ofclaim 25 wherein the reaction is conducted at a temperature of fromabout 600° F. to about 1200° F.
 27. The process of claim 25 wherein thereaction is conducted at a temperature of from about 600° F. to about950° F.
 28. The process of claim 25 wherein the reaction is conducted ata pressure of from about 1 to about 10 atmospheres.
 29. The process ofclaim 25 wherein methane is recovered in continuous fashion from thereactor.
 30. The process of claim 25 wherein carbon dioxide is added tothe reactor as a source of carbon.
 31. The process of claim 25 whereinwater is removed from the reactor via a recycle gas stream.
 32. Theprocess of claim 25 wherein the water is continuously removed.
 33. Theprocess of claim 25 wherein carbon dioxide is removed via a recycle gasstream.
 34. The process of claim 25 wherein the carbon dioxide iscontinuously removed.